1. Field of the Invention
The invention relates to a composition for forming a resist underlayer film (hereinafter referred to as “resist underlayer film-forming composition”) and a method for forming a pattern.
2. Discussion of the Background
A semiconductor device production process normally includes depositing a plurality of materials (processing target film) on a silicon wafer, and patterning the processing target film to form a desired pattern. When patterning the processing target film, a photosensitive material (resist) is deposited on the processing target film to form a resist film, and a given area of the resist film is exposed. The exposed area or the unexposed area of the resist film is removed by development to form a resist pattern, and the processing target film is dry-etched using the resist pattern as an etching mask.
Such a process utilizes ultraviolet rays (e.g., ArF excimer laser light) as the exposure light source for exposing the resist film. A reduction in line width of large-scale integrated circuits (LSI) has been increasingly desired, and a resolution equal to or shorter than the exposure wavelength may be required.
A process has been studied that forms a resist underlayer film (hereinafter may be referred to as “underlayer film”) on the processing target film, transfers the resist pattern to the underlayer film to form an underlayer film pattern, and transfers the resist pattern to the processing target film using the underlayer film pattern as an etching mask (hereinafter may be referred to as “multilayer resist process”). When using the multilayer resist process, it is desirable that the underlayer film be formed of a material that exhibits etching resistance. For example, a composition that contains a polymer that has a side-chain alkynyloxy group has been proposed as a material for forming such an underlayer film (see Japanese Patent Application Publication (KOKAI) No. 2009-014816).
It is necessary to embed depressions formed in a topological substrate when forming a pattern using lithography. In this case, an underlayer film material may be applied, and the resulting film may be planarized.
When forming a flat film on a topological substrate, it is necessary to increase the fluidity of the composition used to form the film. Therefore, it is desirable that the polymer included in the composition have a low molecular weight.